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Enabling Technologies for IMT-Advanced Networks

In Chapter 1, we discussed the various requirements made by the ITU-R for the IMT-Advanced networks. To realize these requirements, IMT-Advanced technologies need to exploit advances at both the architectural (core) network and the access levels. In this chapter, we review the recent advances at the access level that will be used by the IMT-Advanced networks. These will be referred to when discussing the various functionalities in either IMT-Advanced technologies, that is, LTE-Advanced and WiMAX. However, the treatment given here is far from being comprehensive, and only aims at introducing the fundamentals and the envisioned potentials of these advances.

This chapter is organized as follows. Section 2.1 discusses the fundamentals of multicarrier digital modulation. In particular, it discusses the Orthogonal Frequency Division Multiplexing (OFDM) and two multiple access versions of it, namely Orthogonal Frequency Division Multiple Access (OFDMA) and Single-Carrier Frequency Division Multiple Access (SC-FDMA). Next, Section 2.2 discusses multiuser diversity and scheduling. Adaptive Coding and Modulation (ACM) and how it enables a channel-dependent transmission process are discussed in Section 2.3. Section 2.4 addresses the concept of Frequency Reuse (FR) and its different scenarios. Enabling wideband transmissions using carrier aggregation is studied in Section 2.5, while Section 2.6 focuses on Multiple Input Multiple Output (MIMO) techniques. Relaying and the use of femtocells are studied in Sections 2.7 and 2.8, respectively, while Section 2.9 describes the novel Coordinated Multi-point (CoMP) techniques. The widely used power management techniques are highlighted in Section 2.1, while Section 2.11 concludes by talking about inter-technology handovers.